The answer to your question is "it depends". Mainly on your level of involvement in your portfolio and what your goals are in life. Also is your account qualified or non-qualified (taxable vs non-taxable). So there's no one-size-fits-all.
Personally, I am a "set it and forget it" kind of person. You can buy a low-cost target date mutual fund that takes care of all the portfolio management under the hood. If this is in a taxable account - you may have the benefit of tax free portfolio management (Youll have to check if the fund has paid or could pay out capital gains that would be taxable).
Ultimately on a long timescale I wouldn't get distracted by the side shows (highly focused thematic funds). Bet on broad diversification with low management fees and dividend reinvestment and you'll be golden.
Caveat: I dont want to sound overly prescriptive. Again, theres no one-size-fits-all solution.